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Urinary Bladder - Metaplasia

Image of metaplasia in the urinary bladder from a female F344/N rat in a chronic study
Diffuse squamous metaplasia and keratinization of hyperplastic urothelium from a female F344/N rat in a subchronic interim study.
Figure 1 of 4
Image of metaplasia in the urinary bladder from a female F344/N rat in a chronic study
Squamous metaplasia and keratinization from a female F344/N rat in a 40-week interim study.
Figure 2 of 4
Image of metaplasia in the urinary bladder from a female F344/N rat in a chronic study
Squamous metaplasia with and without keratinization, from a female F344/N rat in a subchronic interim study.
Figure 3 of 4
Image of metaplasia in the urinary bladder from a female F344/N rat in a chronic study
Mucinous metaplasia (arrows) characterized by mucinous cells in areas of urothelial hyperplasia, from a female F344/N rat in a chronic study.
Figure 4 of 4
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comment:

Metaplasia of the urothelium reflects the potential of the urothelium to undergo a metaplastic change under a variety of conditions. Squamous metaplasia, with or without keratinization, is the most common variant observed ( Figure 1image opens in a pop-up window , Figure 2image opens in a pop-up window and , Figure 3image opens in a pop-up window ). Mucinous, glandular, or mixtures of metaplastic lesions are less commonly observed ( Figure 4image opens in a pop-up window ).

recommendation:

Urothelial metaplasia and, in particular, the type of metaplasia should be diagnosed and given a severity grade when it becomes a major part of a lesion, for instance, in association with inflammation or hyperplasia. Small or focal lesions, when part of a primary lesion such as chronic inflammation and/or hyperplasia, should not be diagnosed separately.

references:

Gaillard ET. 1999. Ureter, urinary bladder and urethra. In: Pathology of the Mouse: Reference and Atlas (Maronpot RR, Boorman GA Gaul BW, eds). Cache River Press, Vienna, IL, 235-258.
Abstract: http://www.cacheriverpress.com/books/pathmouse.htm

Jokinen MP. 1990. Urinary bladder, ureter, and urethra. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, 109-126.
Abstract: http://www.ncbi.nlm.nih.gov/nlmcatalog/9002563